In recent years, improved light emitting diodes (LEDs) have become available that produce relatively high intensities of output light. These higher power LEDs, for example, have enabled use of LEDs in light fixtures and the like. The improving capability of LEDs and the decreasing cost of the LEDs is making LED based lighting a viable alternative to more traditional lighting, such as incandescent and florescent lights, and will soon allow LED lighting to surpass such older technologies.
For many lighting applications, the LED based fixture incorporates a circuit board supporting and providing electrical connections to a number of individually packaged LEDs. Often the LEDs are arranged in a fairly tight matrix array (see e.g. U.S. Pat. No. 6,016,038), although a variety of other arrangements are known. For example, U.S. Pat. No. 6,995,355 to Rains, Jr. et al. discloses lighting systems using circular or linear arrangements of LED sets as well as rectangular matrix arrangements and other position patterns. In the noted examples, the sets of LEDs have included LEDs configured for emitting different individual colors or wavelengths (e.g. red, green and blue), although the U.S. Pat. No. 6,995,355 patent also suggests inclusion of white LEDs or other white light sources. The red, green and blue light allows adjustment and control of the character of the combined light emitted by the system. As the quality of white LEDs continues to improve, newer lights will utilize similar arrangements of LEDs where all the LEDs are white LEDs.
Today there are many different types of LEDs available, that come in substantially different types of packages and require correspondingly different mounting and electrical connections. Most product lines include LEDs of many different colors, often including white LEDs, all in substantially the same configuration, e.g. with the same kind of housing and the same arrangement of contacts for electrical connection. However, each manufacturer packages their LEDs in a different manner, and many manufacturers offer different LED product lines having different structural configurations.
A printed circuit board for a LED light fixture is designed to match the configuration of one type of LEDs that will be mounted/connected on the board. For example, a board designed for a fixture that will utilize LEDs of a type from one manufacturer (of one color or of a number of different colors) would need to be redesigned in order for the fixture to utilize a different type of LED, such as from a different product line or as might be supplied by a different manufacturer. Also, it is difficult to include structurally different types of LEDs in a single LED set, particularly if the LEDs will be close to each other, because of the need to design different arrangements of contact pads and/or heat sinks on the board to accept each of the different types of LEDs.
Another issue relates to different outputs produced by different types of LEDs. In most lighting applications, it is desirable for the light to appear relatively homogeneous over the area illuminated by the fixture. LEDs usually are point sources. LED fixtures are often designed to reduce the apparent differences in the light output from the different point sources by mixing or combining the light outputs. However, the use of structurally different types of LEDs (e.g. from different manufacturers) often makes that aspect of fixture design more difficult as well.
A need exists for an improved LED board layout and/or improved lighting systems using such a board layout that will improve LED lighting with regard to one or more of the issues outlined above.